Paper Weight Converter: GSM to lb (Bond, Text, Cover, Index)

US basis weight is not a unit — it is the weight of 500 sheets at the grade’s own basic size, and every grade uses a different one. So 20 lb bond, 50 lb text and 28 lb cover are the same paper, and 80 lb cover is nearly twice 80 lb text. This converts either way through the basic size, and handles caliper in points honestly, through a density you can see.

Last updated 24 Sep 2026

Basis weight, grammage and caliper

Seven grades, both directions, plus caliper

What have you got?The first two are exact conversions once you name the grade. The last three are not conversions at all: they go through the paper’s own density, which varies by nearly two to one.

Which grade is it? (this is the whole answer)US basis weight is the weight of 500 sheets at THIS grade’s basic size. Choose the wrong grade and the answer is out by up to a factor of two and a half.

Basis weight (lb)The number printed on the ream wrapper, before the word bond, text, cover, index, tag or bristol.

Grammage (g/m²)The international figure: grams per square metre, the same for every grade, which is why the rest of the world uses it.

Caliper (points, thousandths of an inch)One point of caliper is 0.001 in of thickness. This is a THICKNESS, not a weight, and converting it needs the density below.

Thickness (micrometres)

Pages per inch (PPI)Two pages to a leaf, so PPI = 2 ÷ caliper in inches. Book printers quote PPI because it gives the spine thickness directly.

Finish, for the density the thickness legs needEvery figure here is computed from a published caliper-against-basis-weight table, not assumed. Coated stock is half again as dense as vellum bristol, which is exactly why no fixed points-to-gsm factor can exist.

Density, if you know it (g/cm³)Measure it: grammage divided by caliper. A sheet’s own density is the only honest way to go between thickness and weight.

Not a circuit: the six basic sheet sizes US basis weight is measured on, drawn to scale from one shared corner. This is the whole of the trap in one picture. A pound is a pound, so a ream of the big 25 × 38 in text sheet spreads the same mass over two and a half times the area of the little 17 × 22 in bond sheet — which is why 20 lb bond and 50 lb text are the same paper. Tag and newsprint share the 24 × 36 in sheet, so it is drawn once. The grade you have chosen is drawn with a double line, and the last figure is what that same pound number would mean if the wrapper had said bond.

216.3g/m²Example

80 lb cover — the sheet a business card is cut from

One definition, seven basic sheet sizes

g/m² = lb × 453.59237 ÷ (500 × w × h × 0.00064516) = lb × 1406.14 ÷ (w × h) · caliper → g/m² = caliper_in × 25,400 × density · PPI = 2 ÷ caliper_in

lb: the basis weight: the mass in avoirdupois pounds of 500 sheets at the grade’s basic size
w × h: the grade’s basic size in inches — 17 × 22 for bond, 25 × 38 for text, 20 × 26 for cover, 25½ × 30½ for index, 24 × 36 for tag and newsprint, 22½ × 28½ for bristol
453.59237: grams in a pound, exactly, from the 1959 international agreement
0.00064516: square metres in a square inch, exactly, being 0.0254²
1406.14: the three exact constants collapsed into one. Several trade calculators use 1406.5 instead, which runs 0.026% high
density: the sheet’s apparent density in g/cm³, which is grammage divided by caliper. It is a property of the individual paper, not of the grade, and it is the reason the caliper legs on this page ask you for it

Worked example

80 lb cover — the sheet a business card is cut from
Cover stock is weighed on a 20 × 26 in basic sheet, so its area is 520 in², and 500 of them is 260,000 in²
260,000 in² × 0.00064516 m²/in² = 167.7416 m²; 80 lb × 453.59237 g/lb = 36,287.4 g
36,287.4 ÷ 167.7416 = 216.3 g/m², which is the same as 80 × 2.7041
An 80 lb TEXT sheet, weighed on 25 × 38 in, is 80 × 1.4802 = 118.4 g/m² — the same number on the wrapper, 83% less paper
At the uncoated cover density of 0.766 g/cm³ this sheet is 11.1 points thick, which is 180 pages to the inch

The seven basic sizes, and the factor each one implies

Every figure in the fourth column is computed here from the basic size in the second, not copied from an equivalence table. Bond has the smallest basic sheet and therefore the largest factor; text has the largest sheet and the smallest. The ratio between those two is 2.540, which is the widest any two grades can disagree at the same pound number. Tag and newsprint share a basic size and so share a factor.
Grade	Basic size (in)	Area (in²)	g/m² per lb	Checkpoint	Where you meet it
Bond / writing / ledger / copy paper	17 × 22	374.00	3.7597	20 lb = 75.2 g/m²	20 lb bond, the commonest copier paper
Text / book / offset	25 × 38	950.00	1.4801	80 lb = 118.4 g/m²	80 lb text, a good brochure sheet
Cover	20 × 26	520.00	2.7041	80 lb = 216.3 g/m²	80 lb cover, a business card
Index (index bristol)	25½ × 30½	777.75	1.8080	110 lb = 198.9 g/m²	110 lb index, a record card
Tag	24 × 36	864.00	1.6275	100 lb = 162.7 g/m²	100 lb tag, a luggage label
Bristol (vellum bristol)	22½ × 28½	641.25	2.1928	67 lb = 146.9 g/m²	67 lb vellum bristol, a folder
Newsprint	24 × 36	864.00	1.6275	30 lb = 48.8 g/m²	30 lb newsprint

Common trade weights, and the same sheet read as three other grades

Read across any row and you have the equivalence charts the mills publish, rebuilt from the basic sizes. Neenah Paper’s own guide prints 20 lb bond = 28 lb cover = 42 lb index = 51 lb text = 75 g/m²; this table reproduces that row to within a pound from the sheet dimensions alone, which is the check that the method is right.
Grade	As sold	g/m²	Would be … lb bond	… lb text	… lb cover
Bond / writing / ledger / copy paper	16 lb	60.2	16.0	40.6	22.2
Bond / writing / ledger / copy paper	20 lb	75.2	20.0	50.8	27.8
Bond / writing / ledger / copy paper	24 lb	90.2	24.0	61.0	33.4
Bond / writing / ledger / copy paper	28 lb	105.3	28.0	71.1	38.9
Bond / writing / ledger / copy paper	32 lb	120.3	32.0	81.3	44.5
Text / book / offset	50 lb	74.0	19.7	50.0	27.4
Text / book / offset	60 lb	88.8	23.6	60.0	32.8
Text / book / offset	70 lb	103.6	27.6	70.0	38.3
Text / book / offset	80 lb	118.4	31.5	80.0	43.8
Text / book / offset	100 lb	148.0	39.4	100.0	54.7
Cover	65 lb	175.8	46.8	118.7	65.0
Cover	80 lb	216.3	57.5	146.2	80.0
Cover	100 lb	270.4	71.9	182.7	100.0
Cover	130 lb	351.5	93.5	237.5	130.0
Index (index bristol)	90 lb	162.7	43.3	109.9	60.2
Index (index bristol)	110 lb	198.9	52.9	134.4	73.5
Index (index bristol)	140 lb	253.1	67.3	171.0	93.6
Bristol (vellum bristol)	57 lb	125.0	33.2	84.4	46.2
Bristol (vellum bristol)	67 lb	146.9	39.1	99.3	54.3
Bristol (vellum bristol)	80 lb	175.4	46.7	118.5	64.9
Tag	100 lb	162.7	43.3	110.0	60.2
Tag	125 lb	203.4	54.1	137.4	75.2
Tag	150 lb	244.1	64.9	164.9	90.3
Newsprint	27 lb	43.9	11.7	29.7	16.3
Newsprint	30 lb	48.8	13.0	33.0	18.1
Newsprint	35 lb	57.0	15.2	38.5	21.1

Published caliper against basis weight — and the density each row implies

Basis weight and caliper are Case Paper’s published averages; grammage, density, bulk and PPI are computed from them on this page. The density column is the point: it runs from 0.643 for vellum bristol to 1.227 for gloss coated book, a factor of 1.9, which is why a fixed points-to-gsm factor is fiction. Compare the two coated book rows at 60 lb: same grade, same weight, 12% apart in thickness because one is gloss and one is dull.
Grade and finish	Basis weight	g/m²	Caliper (pt)	Thickness (µm)	Density (g/cm³)	Bulk (cm³/g)	PPI
Forms bond, uncoated	10 lb	37.6	2.00	51	0.740	1.351	1,000
Forms bond, uncoated	15 lb	56.4	3.00	76	0.740	1.351	667
Forms bond, uncoated	20 lb	75.2	4.00	102	0.740	1.351	500
Forms bond, uncoated	24 lb	90.2	4.50	114	0.789	1.267	444
Forms bond, uncoated	28 lb	105.3	5.20	132	0.797	1.255	385
Forms bond, uncoated	32 lb	120.3	6.00	152	0.789	1.267	333
Ledger, uncoated	24 lb	90.2	4.00	102	0.888	1.126	500
Ledger, uncoated	28 lb	105.3	5.00	127	0.829	1.206	400
Ledger, uncoated	32 lb	120.3	6.00	152	0.789	1.267	333
Ledger, uncoated	36 lb	135.4	7.00	178	0.761	1.314	286
Offset / text, regular	50 lb	74.0	4.00	102	0.728	1.373	500
Offset / text, regular	60 lb	88.8	4.50	114	0.777	1.287	444
Offset / text, regular	70 lb	103.6	5.00	127	0.816	1.226	400
Offset / text, regular	80 lb	118.4	6.00	152	0.777	1.287	333
Offset / text, regular	100 lb	148.0	7.00	178	0.832	1.201	286
Coated book, gloss	60 lb	88.8	2.90	74	1.206	0.829	690
Coated book, gloss	70 lb	103.6	3.50	89	1.165	0.858	571
Coated book, gloss	80 lb	118.4	3.80	97	1.227	0.815	526
Coated book, gloss	100 lb	148.0	4.80	122	1.214	0.824	417
Coated book, dull	60 lb	88.8	3.25	83	1.076	0.930	615
Coated book, dull	70 lb	103.6	3.70	94	1.102	0.907	541
Coated book, dull	80 lb	118.4	4.25	108	1.097	0.912	471
Coated book, dull	100 lb	148.0	5.40	137	1.079	0.927	370
Cover, uncoated	65 lb	175.8	9.00	229	0.769	1.301	222
Cover, uncoated	80 lb	216.3	11.50	292	0.741	1.350	174
Cover, uncoated	100 lb	270.4	13.50	343	0.789	1.268	148
Cover, gloss coated	60 lb	162.2	5.50	140	1.161	0.861	364
Cover, gloss coated	65 lb	175.8	6.00	152	1.153	0.867	333
Cover, gloss coated	80 lb	216.3	7.50	191	1.136	0.881	267
Cover, gloss coated	100 lb	270.4	9.50	241	1.121	0.892	211
Cover, gloss coated	120 lb	324.5	12.00	305	1.065	0.939	167
Cover, dull coated	80 lb	216.3	8.50	216	1.002	0.998	235
Cover, dull coated	100 lb	270.4	11.00	279	0.968	1.033	182
Vellum bristol	57 lb	125.0	7.00	178	0.703	1.423	286
Vellum bristol	67 lb	146.9	9.00	229	0.643	1.556	222
Vellum bristol	80 lb	175.4	10.00	254	0.691	1.448	200
Index	90 lb	162.7	7.00	178	0.915	1.093	286
Index	110 lb	198.9	9.00	229	0.870	1.149	222
Index	140 lb	253.1	11.00	279	0.906	1.104	182
Tag	100 lb	162.7	7.00	178	0.915	1.092	286
Tag	125 lb	203.4	9.00	229	0.890	1.124	222
Tag	150 lb	244.1	11.00	279	0.874	1.145	182
Tag	175 lb	284.8	13.00	330	0.863	1.159	154
Tag	200 lb	325.5	15.00	381	0.854	1.171	133

Why the pound number on the wrapper is not a weight

US basis weight is the mass of 500 sheets — at a size that changes with the grade. That is the whole of it, and it is the reason the numbers look absurd. Bond, writing and ledger papers are weighed as a ream of 17 × 22 in sheets. Book, text and offset papers are weighed as a ream of 25 × 38 in sheets, which is two and a half times the area. Cover is weighed on 20 × 26, index on 25½ × 30½, tag and newsprint on 24 × 36, bristol on 22½ × 28½. Each basic size carries its own conversion factor, and the factors run from 1.4802 g/m² per pound for text to 3.7597 for bond. Divide those and you get 2.540: two sheets carrying the same pound number can differ by a factor of two and a half in the amount of paper you are actually holding.

The famous case is cover against text. 80 lb cover is 216 g/m² and you can stand a business card up in it. 80 lb text is 118 g/m² and it is a brochure sheet. Same eighty, nearly double the paper. Going the other way, 20 lb bond, 50 lb text and 28 lb cover are all about 75 g/m² — the same sheet under three labels — which is precisely the equivalence a mill’s chart exists to state and this page computes from the sheet dimensions. Grammage has no such problem: a square metre is a square metre whatever the grade, and that is the only reason the rest of the world’s paper is easier to buy.

Now the part most converters get wrong: caliper. A caliper in “points” is a thickness — one point is 0.001 in — and thickness and weight are joined only by the sheet’s own density. Across the eleven published grade-and-finish combinations in the table above, apparent density runs from 0.643 g/cm³ for vellum bristol to 1.227 for gloss coated book: a factor of 1.9. Copresco’s example is sharper still — Cougar Opaque 60 lb text measures 4.6 points in the smooth finish and 5.2 in the vellum, one grade and one basis weight 13% apart in thickness, because calendering squeezes air out of the sheet. So this page asks you which finish you have, shows you the density it is using, and lets you overwrite it. It does not publish a points-to-gsm factor, because there is no such number.

Pages per inch, and the spine. Book printers quote PPI rather than caliper because it answers the question they actually have: divide the page count by the PPI and you have the block thickness in inches. There are two pages to a leaf, so PPI = 2 ÷ caliper in inches, which is why Case Paper’s worked example reads 2 ÷ 0.0095 = 211 PPI for 100 lb gloss cover. A 320-page book on 80 g/m² uncoated text stock runs about 16 mm of block, and the same book on a bulkier antique-finish sheet of the same grammage runs a fifth thicker — which is how publishers make a thin book look substantial without adding a word.

What this page leaves out. No M weight, which is the mass of 1,000 sheets at a stated cut size rather than the basic size, and is a price unit rather than a paper property. No opacity, brightness or bursting strength: those are the specifications that actually decide whether a sheet is fit for a job, and none of them follows from grammage. And no tissue: a tissue ream is 480 sheets, not 500, so the whole definition shifts under it. For the sheet sizes these weights are cut to, see the paper size converter; for the resolution to print on them, the DPI and print size calculator. This unit is not the same size everywhere. The value used here is stated below; confirm which local definition applies to your document before you rely on the figure.

Frequently asked questions

What is 80 lb paper in gsm?

It depends entirely on the grade, and that is not a dodge — it is the answer. 80 lb cover is 216 g/m². 80 lb text is 118 g/m². 80 lb index is 145 g/m², 80 lb bristol 175 g/m², 80 lb tag 130 g/m². If a quote says “80 lb” without naming the grade it has told you nothing, and the spread is nearly two to one.

Is 20 lb bond the same as 50 lb text?

Yes, to within a pound. 20 lb bond is 75.2 g/m² and 50 lb text is 74.0 g/m². Neenah Paper’s own equivalence chart prints 20 lb bond = 51 lb text = 28 lb cover = 42 lb index = 75 g/m², and those four all fall between 75.2 and 75.9 g/m² when computed from the basic sizes. They are the same sheet with four labels.

How do I convert points of caliper to gsm?

You cannot, without knowing the paper. Caliper is thickness and grammage is mass per area; the bridge between them is apparent density, which runs from about 0.64 g/cm³ for vellum bristol to about 1.23 for gloss coated book — a factor of 1.9. Measure your own sheet (grammage ÷ caliper), or pick the finish above and accept that the answer carries that uncertainty. A single published points-to-gsm factor is one paper’s density with the choice hidden.

Why is US paper weight measured this way at all?

Because it started as a mill’s own stock-keeping figure: how much does a ream of what I make weigh? Each trade made its own sheet, so each trade’s ream weight was measured on its own sheet, and the numbers were never meant to be compared across trades. They still are not comparable; grammage was invented to fix exactly that.

What is pages per inch and how does it relate to caliper?

PPI is 2 ÷ caliper in inches, because a leaf of paper carries two pages. A 0.0046 in sheet is 435 PPI, so a 320-page book on it has a 0.74 in block. Book printers quote PPI rather than caliper because the spine width is what they need, and the cover has to be made before the pages are printed.

Is 300 gsm card the same as 110 lb index?

No. 110 lb index is 199 g/m². 300 g/m² is about 111 lb cover, 166 lb index or 203 lb text. The card people mean when they say “300 gsm” is usually sold in the US as 110 lb cover, which is 297 g/m² — close, but arrived at from the other direction.

Does a heavier sheet always feel thicker?

No, and this is where the two systems really separate. Grammage is mass and caliper is thickness, and coating adds a lot of the first for very little of the second. A 100 lb gloss coated cover sheet is 270 g/m² and 9.5 points; a 100 lb uncoated cover sheet is the same 270 g/m² and 13.5 points, forty per cent thicker. If what you want is stiffness, specify caliper.

Related calculators

References

Wikipedia, Grammage (read 26 September 2026), for the definition of US basis weight as the weight of a 500-sheet ream at the grade’s basic size, and for the basic sizes of bond/writing/ledger (17 × 22 in), book/text/offset (25 × 38 in), cover (20 × 26 in) and newsprint (24 × 36 in). It also records that a tissue ream is 480 sheets rather than 500, which is why a “ream” is not a fixed count.
PrintWiki, Basic Size (printwiki.org/Basic_Size, read 26 September 2026): “for book paper it is 25 × 38, for bond paper it is 17 × 22, for cover paper it is 20 × 26, for bristol paper it is 22½ × 28½, for index paper it is 25½ × 30½, and for tag paper it is 24 × 36.” This is the second, independent source for the six basic sizes this page computes from.
Neenah Paper, Basis Weights (neenahpaper.com/resources/paper-101/basis-weights, read 26 September 2026) — a mill’s own guide. “Basis weight equals the ream (500 sheet) weight of the base size”, with base sizes for bond, cover, index, bristol and text, and the worked equivalence 20 lb bond = 28 lb cover = 42 lb index = 51 lb text = 75 g/m². This page reproduces that row to within a pound from the basic sizes alone.
Case Paper, Paper Thickness tables (casepaper.com/resources/paper-price-calculators/paper-thickness/, read 26 September 2026): average caliper against basis weight for eleven grade-and-finish combinations. Every apparent density on this page is computed from those rows, and the spread they imply — 0.64 to 1.23 g/cm³ — is why the caliper conversion needs a density input instead of a fixed factor.
Case Paper, Pages per Inch Calculator (casepaper.com, read 26 September 2026), for the definition PPI = 2 ÷ caliper in inches, with the worked example 2 ÷ 0.0095 = 211 PPI for 100 lb gloss coated cover. Two pages per leaf is the whole of the factor of two.
Copresco, Confused About Paper Caliper, Points and PPI? (copresco.com/lite12/0712ltx.htm, read 26 September 2026). Defines caliper as thickness in thousandths of an inch and gives the case this page leans on: Cougar Opaque 60 lb text measures 4.6 points smooth and 5.2 points vellum — one grade, one basis weight, 13% apart in thickness.
Horizon Paper, Basis Weight to Grammage Calculator (horizonpaper.com, read 26 September 2026), which uses the single constant 1406.5 divided by the basic sheet area in square inches. The exact constant is 1406.14 — 453.59237 g per pound divided by 500 sheets and by 0.00064516 m² per square inch — so that tool runs 0.026% high. This page uses the exact figure.
National Institute of Standards and Technology, Refinement of Values for the Yard and the Pound, Federal Register notice of 1 July 1959, which fixed the international inch at exactly 25.4 mm and the avoirdupois pound at exactly 0.45359237 kg. Both exact values are used throughout this batch; every inch-to-millimetre figure here is therefore exact, not approximate.